Structured Output From Local LLMs: JSON That Never Breaks (Ollama + Zod) (opens in new tab)

A 1.5B model running on your laptop will return JSON that almost parses. The closing brace is missing. A trailing comma sneaks in. The whole thing is wrapped in a markdown fence with a chirpy "Sure! Here's your JSON:" on top. Cloud models do this too, but small local models do it constantly, and that is exactly where most "just prompt it harder" advice falls apart. I wrote about validating LLM responses with Zod before: schemas as contracts, safeParse, extracting JSON from chaos. That post is...